Not long ago, a Manhattan rabbi stunned his congregants by informing them that the future of the Jewish people would be secured not through trips to Israel, not through the battle against anti-Semitism, and not through the continued upward mobility of Jews, but in the bedroom. What shocked his sophisticated Upper East Side audience had nothing to do with his allusion to sex; these days, it is perfectly acceptable to speak in public about intimate behavior. What is not permissible in polite Jewish company is an allusion to the decisions people make about their own family lives, or to the impact of those decisions on the ability of the Jewish community to sustain itself.

It is not as if the contours of today’s demographic crisis are hidden from view. “American Jews See Population, Birthrate Drop,” screamed a recent headline in the Los Angeles Times...............